Currently, the treatment of diabetes, both type 1 diabetes and type 2 diabetes, relies to an increasing extent on the so-called intensive insulin treatment. According to this regimen, the patients are treated with multiple daily insulin injections comprising one or two daily injections of long acting insulin to cover the basal insulin requirement supplemented by bolus injections of a rapid acting insulin to cover the insulin requirement related to meals.
Long acting insulin compositions are well known in the art. Thus, one main type of long acting insulin compositions comprises injectable aqueous suspensions of insulin crystals or amorphous insulin. In these compositions, the insulin compounds utilized typically are protamine insulin, zinc insulin or protamine zinc insulin.
Certain drawbacks are associated with the use of insulin suspensions. Thus, in order to secure an accurate dosing, the insulin particles must be suspended homogeneously by gentle shaking before a defined volume of the suspension is withdrawn from a vial or expelled from a cartridge. Also, for the storage of insulin suspensions, the temperature must be kept within more narrow limits than for insulin solutions in order to avoid lump formation or coagulation.
Another type of long acting insulin compositions are solutions having a pH value below physiological pH from which the insulin will precipitate because of the rise in the pH value when the solution is injected. A drawback with these solutions is that the particle size distribution of the precipitate formed in the tissue on injection, and thus the release profile of the medication, depends on the blood flow at the injection site and other parameters in a somewhat unpredictable manner. A further drawback is that the solid particles of the insulin may act as a local irritant causing inflammation of the tissue at the site of injection.
Human insulin has three primary amino groups: the N-terminal group of the A-chain and of the B-chain and the ε-amino group of LysB29. Several insulin derivatives which are substituted in one or more of these groups are known in the prior art. Thus, U.S. Pat. No. 3,528,960 (Eli Lilly) relates to N-carboxyaroyl insulins in which one, two or three primary amino groups of the insulin molecule has a carboxyaroyl group.
According to GB Patent No. 1.492.997 (Nat. Res. Dev. Corp.), it has been found that insulin with a carbamyl substitution at NεB29 has an improved profile of hypoglycemic effect.
JP laid-open patent application No. 1-254699 (Kodama Co., Ltd.) discloses insulin wherein a fatty acid is bound to the amino group of PheB1 or to the ε-amino group of LysB29 or to both of these. The stated purpose of the derivatisation is to obtain a pharmacologically acceptable, stable insulin preparation.
Insulins, which in the B30 position have an amino acid having at least five carbon atoms which cannot necessarily be coded for by a triplet of nucleotides, are described in JP laid-open patent application No. 57-067548 (Shionogi). The insulin analogues are claimed to be useful in the treatment of diabetes mellitus, particularly in patients who are insulin resistant due to generation of bovine or porcine insulin antibodies.
WO 95/07931 (Novo Nordisk A/S) discloses human insulin derivatives wherein the ε-amino group of LysB29 has a lipophilic substituent. These insulin derivatives have a prolonged profile of action and are soluble at physiological pH values.
EP 894095 discloses insulin derivatives wherein the N-terminal group of the B-chain and/or the ε-amino group of Lys in position B28, B29 or B30 has a substituent of the formula —CO—W—COOH where W can be a long chain hydrocarbon group. These insulin derivatives have a prolonged profile of action and are soluble at physiological pH values.
Unfortunately, many diabetics are unwilling to undertake intensive therapy due to the discomfort associated with the many injections required to maintain close control of glucose levels. This type of therapy can be both psychologically and physically painful. Upon oral administration, insulin is rapidly degraded in the gastro intestinal tract and is not absorbed into the blood stream. Therefore, many investigators have studied alternate routes for administering insulin, such as oral, rectal, transdermal, and nasal routes. Thus far, however, these routes of administration have not resulted in effective insulin absorption.
Efficient pulmonary delivery of a protein is dependent on the ability to deliver the protein to the deep lung alveolar epithelium. Proteins that are deposited in the upper airway epithelium are not absorbed to a significant extent. This is due to the overlying mucus which is approximately 30-40 μm thick and acts as a barrier to absorption. In addition, proteins deposited on this epithelium are cleared by mucociliary transport up the airways and then eliminated via the gastrointestinal tract. This mechanism also contributes substantially to the low absorption of some protein particles. The extent to which proteins are not absorbed and instead eliminated by these routes depends on their solubility, their size, as well as other less understood characteristics.
It is however well recognised that the properties of peptides can be enhanced by grafting organic chain-like molecules onto them. Such grafting can improve pharmaceutical properties such as half life in serum, stability against proteolytical degradation, and reduced immunogenicity.
The organic chain-like molecules often used to enhance properties are polyethylene glycol-based or polyethylene based chains, i.e., chains that are based on the repeating unit —CH2CH2O—. Hereinafter, the abbreviation “PEG” is used for polyethyleneglycol.
Classical PEG technology takes advantage of providing polypeptides with increased size (Stoke radius) by attaching a soluble organic molecule to the polypeptide (Kochendoerfer, G., et al., Science (299) 884-, 2003). This technology leads to reduced clearance in man and animals of a hormone polypeptide compared to the native polypeptide. However this technique is often hampered by reduced potency of the hormone polypeptides subjected to this technique (Hinds, K., et al., Bioconjugate Chem. (11), 195-, 2000). WO 02/20033 discloses a general method for the synthesis of well defined polymer modified peptides.
However, there is still a need for insulins having a more prolonged profile of action than the insulin derivatives known up till now and which at the same time are soluble at physiological pH values and have a potency which is comparable to that of human insulin. Furthermore, there is need for further insulin formulations which are well suited for pulmonary application.